Method and apparatus for handling metal strip



March 22, 1966 J RANNEY I 3,241,735

METHOD AND APPARATUS FOR HANDLING METAL STRIP Filed Oct. 10, 1963 2Sheets-Sheet 1 FIG.

INVENTOR. NEIL J. RANNEY ATTORNEYS N. J. RANNEY March 22, 1966 METHODAND APPARATUS FOR HANDLING METAL STRIP Filed Oct. 10, 1963 2Sheets-Sheet 2 v R 0 W WM a E A Rw M WR \8! m J. T A E N FIG. 4

United States Patent 3,241,735 METHOD AND APPARATUS FOR HANDLING METALSTRIP Neil J. Ranney, Mentor, Ohio, assignor to Production MachineryCorporation, Mentor, Ohio, a corporation of Ohio Filed Oct. 10, 1963,Ser. No. 315,314 11 Claims. (Cl. 226-4) This invention pertains to theart of processing metal strip and more particularly to a method andapparatus for handling metal strip as it passes through a processingline.

The invention is particularly applicable for handling heavy gauge steelstrip in a processing line for removing oxide scale from the surfaces ofthe strip and it will be described with particular reference thereto;however, it will be appreciated that the invention has much broaderapplications and may be used in various processing lines adapted tohandle any gauge of metal strip.

The term metal strip indicates a strip formed from any metallic materialsuch as steel, iron, copper, aluminum, zinc and tin, to name only a few.

The term processing line as used herein includes apparatus which conveysor guides a metal strip, in uncoiled form, around rolls and throughvarious processing steps, such as heating, cooling, cleaning, coating,hot or cold working, etc., apparatus for initially uncoiling the stripand apparatus for subsequent coiling or otherwise handling the strip.

The terms line tension and line speed as used herein refer to thetension and speed of the metal strip as it moves through the processingline.

In processing metal strip, even if the strip has a somewhat heavy gauge,it is the common practice to hot roll the strip into an intermediatesize strip having a thickness somewhat close to the desired thickness ofthe final strip. This hot rolling operation is carried out in theatmosphere; therefore, an oxide scale forms on the surfaces of the hotrolled strip which scale must be removed before the strip can besatisfactorily progressed through additional processing operations, suchas cold rolling.

To remove the scale from the surfaces of the strip, it hasheretoforebeen common practice to uncoil the hot rolled strip and pass the stripthrough an acid pickling bath after which the strip was again coiled orwas immediately conveyed into a subsequent processing line. The use ofan acid for removing the scale created obvious disadvantages. Forinstance, it was necessary to provide elaborate tanks and piping forhandling the acid. The disposal of .the acid waste was difficult andexpensive because the acid created serious pollution problems whendischarged into streams or sewers. If the acid were first neutralizedbefore disposal, expensive equipment and chemicals were required.

To overcome these disadvantages of using acid in the processing ofstrip, it has heretofore been suggested that the scale could be removedfrom the strip by a physical abrading process wherein both surfaces ofthe strip were subjected to a stream of small steel shot propelledagainst the surfaces by high pressure air or by centrifugal force. Sucha scale removing process would overcome the most prevalent disadvantagesof acid pickling; however, its

use has been limited by the geometry of the strip as it was .was.impinge dudownwardly against the upper surface of the strip and upwardlyagainst the lower surface of the strip. There was no satisfactory way ofremoving all of the scale and shot from the upper surface of the strip,and it was mechanically awkward to blast the lower strip surface.

To overcome this disadvantage, it has been suggested that the strip beconveyed upwardly in a substantially vertical direction so that thesteel shot impinging against the surfaces of the strip would falldownwardly as the strip was moving upwardly. This arrangement wasequally unsatisfactory because the shot and scale tended to drop intothe guide rolls adjacent the bottom of the strip where it caused rapidfailure of the rolls and marred the surfaces of the strip. In order toblast strip in a vertical pass, the blast wheels must be mountedhorizontally, with their axes vertical, and it was found that the gritdid not flow properly with the wheels in this position.

Recently, it has been found that superior results can be obtained byconveying the metal strip in a vertical plane, i.e. edgewise, past theshot blasting apparatus. In this manner, the surfaces of the strip facehorizontally as the strip moves through the shot blasting apparatus andthe residue of the blasting operation drops downwardly away from thestrip. To utilize this vertical plane blasting operation, it has beensuggested that all of the processing line equipment be redesigned tohandle the strip on edge. The existing line equipment could not be usedbecause it was adapted to handle the strip in only a horizontal plane.Such redesign of the line equipment would involve a considerable capitalexpense and it was not necessary for all operations in processing thestrip.

The present invention is directed toward a method and apparatus forhandling metal strip which method and apparatus allow the strip to beconveyed edgewise through a shot blasting operation without requiringthe redesign of the other equipment to handle strip in the edgewiseposition.

Although the use of equipment for conveying strip in an edgewiseposition (which means that the strip is moving in a vertical plane whenmoving parallel to the rolling mill floor) is discussed with specialemphasis on shot blasting, edgewise conveying has other advantages inprocessing thin metal strip. For instance, when the thin strip is beingannealed by passing the strip through a horizontally extending furnace,the furnace must have a substantial length. The long furnace length isdictated by the rapid speed of the strip and the high annealingtemperature of the strip. If the strip is traveling in a horizontal passplane, the strip tends to sag in the long furnace. Intermediate supportrolls within the furnace have not been very satisfactory because theycould not withstand the high furnace temperatures and they tended to marthe surfaces of the heated strip.

To overcome these disadvantages, the furnace could be provided with asubstantial vertical height so that the sag, or catenary, could beaccommodated within the furnace without support rolls. This of coursewas very expensive and required substantial space. Another solution tothe problem was to decrease the catenary by increasing the tension ofthe strip. This often resulted in stretching of the strip, especiallywhen it was relatively thin and was heated to a very high temperature.Since these two solutions had obvious disadvantages, it was suggestedthat the thin strip could be conveyed in a vertical direction through avertically extending furnace. This arrangement was not completelysatisfactory because an upper roll was required in the furnace whichroll could mar the surface of the strip. Even with the upper roll, thenecessary furnace length would require a considerably higher structurethan possible in some rolling mill-s. Also, the weight of the stripwould tend to stretch the heated strip as it was moving through thefurnace.

.spect to the previous pass plane.

All of these disadvantages can be overcome by conveying the thin stripthrough the furnace in an edgewise position since the rigidity of thestrip itself will limit the catenary. A few bottom support-s constructedof heat resistant material which is not susceptible'to deterioration canfurnish the necessary vertical support of the strip without thedisadvantage of guide rolls.

It is obvious that other processing operations may be moresatisfactorily performed with the strip in an edgewise, or vertical passplane.

In accordance with the present invention there is provided a method ofchanging the pass plane of a metal strip moving through a processingline from a first plane to a second plane comprising the steps ofguiding a first section of the strip along the first plane, driving thefirst section at a predetermined line speed and under line tension,guiding a second and subsequent section of the strip along the secondplane, driving the second section at a predetermined line speed andunder line tension, forming a low tension, natural loop in the stripbetween the first and second sections the strip being twisted in theloop between a substantially horizontal and a substantially verticaldisposition, and correlating the speeds of the sections to maintain thenatural loop.

In accordance with another aspect of the present invention, there isprovided an apparatus for changing the pass plane of a metal stripmoving through a processing iine comprising a first and second set ofpinch rolls spaced from each other to define an intermediate pass in theprocessing line, the pinch roll sets being obliquely disposed withrespect to each other to define the desired change in the pass plane,means for controlling the relative speed of the pinch rolls to maintainthe tension in the intermediate pass substantially below the linetension in the processing line. In this manner, the strip moving throughthe intermediate pass can form a natural loop which will allow movementbetween the pinch roll sets without deformation of the strip.

The method and apparatus defined above can be used for changing the passplane of a metal strip from a horizontal pass plane to a vertical passplane for moving the strip edgewise through a processing operation whichmay be more expeditiously performed with the strip on edge. Such anoperation is shot blasting of the strip to remove oxide scale.

It will be appreciated that the invention may be used for changing thepass plane of metal strip between various planes and not necessarilybetween a horizontal and vertical plane. Essentially, the presentinvention allows a shift in the pass plane of a strip traveling througha processing line so that the new pass plane is oblique with re- Theterm oblique ndicates that the shift in pass plane is not just a change1n direction as found when a strip in a horizontal pass plane is shiftedaround a roll into an upwardly extending pass plane or into anotherhorizontal pass plane parallel with the first plane. Consequently, theinvention relates to shifting the pass plane of the metal strip in avariety of combinations with the exception of those changes indtcatedabove.

The primary object of the present invention is the prov1s1on of a methodand apparatus for shifting the pass plane of a metal strip movingthrough a processing line from a first plane to a second plane obliqueto the first plane.

Another object of the present invention is the provision of a method andapparatus for shifting the pass plane of a metal strip moving through aprocessing line from a first plane to a second plane oblique to thefirst plane which method and apparatus does not plastically distort themetal strip.

Another object of the present invention is the provision of a method andapparatus for shifting the pass plane of a metal strip moving through aprocessing line from a first plane to a second plane oblique to thefirst plane which method and apparatus include the formation andmaintenance of a natural, low tension loop between the two planes.

Yet another object of the present invention is the provision of a methodand apparatus for shifting the pass plane of ametal strip moving througha processing line from a first plane to a second plane oblique to thefirst plane wherein the length of the processing line required for theshift in the pass plane is minimized.

Yet a further object of the present invention is the provision of amethod and apparatus for shifting the pass plane of a metal strip movingthrough a processing line from a first plane to a second plane obliqueto the first plane which includes the formation and maintenance of anatural, low tension loop between the two planes and wherein the lengthof all longitudinally extending lines in the strip of the loop aresubstantially the same.

These and other objects and advantages will become apparent from thefollowing description used to illustrate the preferred embodiment of thepresent invention as read in connection with the accompanying drawingsin which:

FIGURE 1 is a side elevational, schematic view illustrating thepreferred embodiment of the present invention wherein the change in passplane is between horizontal and vertical planes without a change in thedirection of movement of the metal strip;

FIGURES 2 and 3 are partial, schematic, views illustrating modificationsof the embodiment shown in FIG- URE 1 wherein the strip is shifted froma horizontal to a vertical pass plane with the direction of the stripbeing reversed; and

FIGURE 4 is a partial, schematic view illustrating a modification of thepresent invention wherein the pass plane is shifted from horizontal tovertical and the direction of the moving strip is changed int-oapproximately a right angle.

Referring now to the drawings wherein the showings are for the purposeof illustrating a preferred embodiment of the invention only and not forthe purpose of limiting same, FIGURE 1 shows a processing line A forremoving oxide scale from metal strip B. The metal strip is directedthrough the processing line from a coil 10 which is supported onto anappropriate apparatus such as a processing uncoiler (not shown). At theopposite end of the line there is provided a take-up roll 12 whichrecoils the metal strip -B as it comes from the processing line. It isappreciated that the take-up coil 12 may be replaced by a subsequentprocessing line so that the strip B can progress from processing line Ainto a subsequent line for cold rolling, annealing or similaroperations. Usually, the coil 10 is mounted on an apparatus which shearsthe trailing end of the coil and welds the leading end of another coilthereto so that the strip B as it progresses through line A issubstantially continuous.

Within the processing line A there are provided a plurality of pinchroll sets 20, 22, 24 and 26 which divide the strip B into (a) pass 30which is in a horizontal plane i.e. the large flat surfaces facevertically, (b) a first intermediate pass 32 (0) pass 34 which is in asubstantially vertical plane, i.e. the large surfaces face horizontally,(d) a second intermediate pass 36, and (e) pass 38 which is in ahorizontal plane similar to the plane of pass 30.

The pinch rolls 20, 22 definethe intermediate pass 32 and these rollsare obliquely positioned with respect to each other. This indicates thatthe nip of each pinch roll set is in a plane not coinciding with theplane of the .other set and not parallel with the other set. Thus, the

distances between corresponding points on the nip of the obliquelyarranged pinch roll sets 20, 22 vary. This same general discussionapplies to obliquely arranged pinch rol-l sets 24, 26 which define thesecond intermediate pass 36.

In the pass 30 there is provided a conventional five roll leveler 40which is adapted to pull the strip B from coil and flex the strip into aflat configuration. The leveler 40 is driven by an appropriatemechanism(not shown) so that the strip B moves through the processing line A atthe desired speed and under a desired line tension. In accordance withone embodiment of the present invention, the strip B is 72 inches wideand A inch thick with a force applied of 9,000 pounds in a directionlongitudinal of the strip. Consequently, the strip has approximately 500lbs/in. of tension applied as it is moving through the processing linein horizontal pass 30. It is appreciated that auxiliary guide rolls anddrive rolls may be used in the horizontal pass 30 to convey the strip Bfrom coil 10 to pinch roll set 20 under the proper tension and in theproper position. I

The strip B is in a vertical plane pass 34 which vertical plane greatlyenhances the characteristics of certain line operations such as,with-out limitation, shot blasting the opposite surfaces of the strip toremove oxide scale which formed while the strip was being hot rolled.Shot blasting unit 50 is schematically represented and includes aplurality of heads 52 which direct, by air or centrifugal force, amyriad of small steel shot against the opposite surfaces of the stripwhich shot abrades the strip and removes the oxide scale. With the stripin a vertical plane, i.e. edgewise, the shot easily drops from the stripbefore the strip enters the nip of pinch roll set 24. Although the pass34 is defined as vertical, it is appreciated that the strip need not beexactly 90 with respect to horizontal and that various lesser degrees ofinclination with horizontal would function satisfactorily. Thes-peed ofstrip B in pass 34 is the same as the speed of strip B in all otherportions of the line and a line tension is applied to the strip in thispass.

In the horizontal pass 38, the take-up roll 12 or a subsequentprocessing operation can be used, as was previously described. Again,the speed of the strip in pass 38 is the same as the speed in otherportions of the processing line and the strip is under line tension sothat it can be conveniently conveyed to the subsequent operations.

The present invention pertains to a method and apparatus for shiftingthe pass plane of strip B as it moves through line A and, in accordancewith the illustrated embodiment of the present invention, the pass planeis shifted from a horizontal plane in pass 30 to a vertical plane inpass 34. It is appreciated that other oblique shifts in the pass planeof the strip could be made by utilizing the present invention. The shiftis accomplished in the first intermediate pass 32 and the apparatus andmethod for accomplishing the shift will be described in detail. It is tobe appreciated that this discussion will apply equally to the apparatusand method for shifting the pass plane of strip B between pass 34 andpass 38, which is not described.

As previously explained, roll sets 20, 22 which define intermediate pass32, are obliquely positioned with respect to each other. In accordancewith the illustrated embodiment of the invention, roll set 20 is drivenby a wound rot-or motor 60 having primary power lines 62, 64 .and 66with a secondary circuit speed control '68 of conventional construction.The output :of motor 60 is physically connected to the roll set 20 by anappropriate mechanism, schematically represented as line 70. By thisconstruction, variations in control 68 changes speed of motor 60 and,thus, the speed of roll set 20.

In a similar manner, wound rotor motor 80 having primary power lines 82,84 and 86 and a secondary circuit speed control 88 is coupled by shaft90 onto the roll set 22. The motors 60, 80 can be adjusted tosynchronize the speed of roll sets 20, 22 and also to adjust for anydifference in the speeds of the spaced roll sets.

To control the secondary speed controls 68, 88 there is provided asensing device 100 which, in accordance with the illustrated embodimentof the present invention, is a feeler which is conected to a control102. Changes in the position of the feeler 100 causes a signal to begenerated by control 102 which signal is furnished to motors 60, bycontrol lines 104, 106, respectively. Thus, the position of feelercontrols the speed of motors 60, 80.

In operation of the present invention, the strip B is threaded throughthe processing line A and a natural loop Cis provided in the stripbetween the pinch roll set 20 and the pinch roll set 22. The termnatural loop as used herein indicates that the length of the strip Bbetween roll sets 20, 22 is substantially greater than the spacingbetween these sets which spacing is represented by a and that the excessin strip length is allowed to take a natural shape which, in practice,has been found to produce a loop wherein no part of the strip isdistorted beyond its elastic limit. The speed of roll sets 20, 22 is sosynchronized that there is no substantial tension in the natural loop C,except for the tension caused by the weight of the loop itself. The sizeof the natural loop is determined somewhat by the width and thickness ofthe material and the material itself; and the loop is sufficiently largeto prevent stretching of any portion of the strip as it progresses frompass 30 to pass 34. The term natural loop does not exclude guide rollsto form the path of the loop or to support certain parts of the loop.Primarily, the natural loop must be so formed that stretching andkinking of the strip is prevented;

The size of the natural loop C is maintained, in ac cordance with theillustrated embodiment of the present invention, by the feeler 100. Whenthe feeler senses a decrease in the size of the natural loop C, thelinear speed of roll set 20 is increased with respect to the linearspeed of roll set 22. This can be accomplished by increasing the speedof motor 60 or decreasing the speed of motor 80 or a combination ofthese actions. The control 102 adjusts the speed of motors 60, 80 toincrease the length of the loop so that the desired size can bemaintained. If the feeler senses an increase in the loop over apredetermined maximum, the speed of roll set 22 must be increased withrespect to the speed of roll set 20; therefore, the appropriateadjustment of motors 60, 80 is effected by the control 102.

It is appreciated that one of the roll sets 20, 22 may be driven at aconstant speed and the other roll set could then be adjusted to increaseor decrease the size of the natural loop C without departing from theintended spirit and scope of the present invention. It is also withinthe scope of the invention to provide various sensing devices such asphotoelectric cells, gas jets, proximity switches, etc.

Referring now to FIGURES 2 and 3, there is illustrated a method andapparatus for shifting the pass plane of metal strip B from a horizontalpass 124 to a vertical pass 126 in a manner quite similar to the methodand apparatus illustrated in FIGURE 1; however, the vertical pass 126 isreversed in direction from the horizontal pass 124. It is readily seenthat the present invention is adapted to change the pass plane of thestrip B and also to change the general direction of the strip. Roll sets120, 122 separate the intermediate pass 128 from horizontal pass 124 andvertical pass 126. Motors 130, 132 control the roll sets in accordancewith a signal from sensing device 134.

The natural loop D of FIGURE 2 and natural loop E of FIGURE 3 areformed'between the roll sets 120, 122 so that there is substantially notension in these natural loops except for the tension caused by theweight of the strip B. Natural loop D is formed by bringing the loweredge of strip B in pass 124 to the uppermost part of pinch roll set 122.This natural loop diifers from the natural loop E shown in FIGURE 3wherein the lower edge of strip B in pass 124 is brought to thelowermost edge of pinch roll set 122. It is appreciated that thediiference between these two natural loops is minor and the apparatusoperates the same although there may be some advantage in certaininstances in bringing a certain edge of the strip to the top of thevertical pass 126.

Referring now to FIGURE 4, the horizontal pass 140 is substantiallyperpendicular to the vertical pass 142 so that the intermediate pass 144between pinch roll sets 146, 148 is utilized in drastically changing thedirection of the strip B while also changing the pass plane of thestrip. Motors 150, 152 are controlled by a sensing device 154 tomaintain the proper shape of the natural loop F. In this embodiment, thenatural loop is formed into approximately a 180 bend and then into areversed 90 bend. At each of these bends, the natural loop must beformed so that there is no stretching or kinking of the strip. Ofcourse, that exact path of the loop can be controlled to a certainextent by guide rolls and similar apparatus without destroying thecharacteristics of the natural loop. It is appreciated that the naturalloop may be formed to bring either edge of the strip to the top of pinchroll 148. This reversal of the strip is easily accomplished in the otherembodiments of the invention.

It is appreciated that various changes may be made in the illustratedembodiments of the present invention without departing from the intendedspirit and scope of the present invention as defined in the appendedclaims.

Having thus described my invention, I claim:

1. A method of changing the pass plane of a metal strip moving through aprocessing line from a first plane to a second plane oblique to saidfirst plane comprising the steps of guiding a first section of saidmetal strip along said first plane, driving the first section of metalstrip at a predetermined line speed and under line tension, guiding asecond and subsequent section of said metal strip along said secondplane, driving said second section of said metal strip at apredetermined line speed and under line tension, forming a low tensionnatural loop in said metal strip between said sections,with said stripbeing twisted in said loop between a substantially horizontal and asubstantially edgewise disposition and correlating the speeds of saidsections to maintain said natural loop.

2. A method of changing the pass plane of a metal strip moving through aprocessing line from a first plane to a second plane oblique to saidfirst plane comprising the steps of providing two sets of pinch rollswith the nip of one set substantially in the first plane and the nip ofsaid second set substantially in the second plane, driving the rolls atsubstantially the same linear surface speed, forming the metal stripbetween said roll sets into a natural loop wherein the length of thestrip between the rolls is substantially greater than the length of astraight line extending between the nips of the roll sets and with saidstrip being twisted in said loop between a substantially horizontal anda substantially edgewise disposition, and controlling the speed of theroll sets to maintain this greater length of the metal strip between theroll sets.

3. A method of processing metal strip comprising conveying said metalstrip in a horizontal pass plane to a set of substantially horizontalpinch rolls, forming a natural loop in said metal strip as it leavessaid pinch roll set, terminating said natural loop at a substantiallyvertical set of pinch rolls, controlling the speed of said pinch rollsets to maintain said natural loop at a predetermined size and undervery little tension, and then passing said metal strip in an edgewiseposture through a processing operation.

4. A method of processing metal strip comprising conveying said metalstrip in a horizontal pass plane to a set of substantially horizontalpinch rolls, forming a natural loop in said metal strip as it leavessaid pinch roll set, terminating said natural loop at a substantialvertical set of pinch rolls, controlling the speed of said pinch rollset to maintain said natural loop at a predetermined size and under verylittle tension, passing said metal strip in an edgewise posture througha processing operation to a second set of vertical pinch rolls, forminga second natural loop in said metal strip as the metal strip leaves saidsecond vertical pinch roll set, terminating said second natural loop ata second substantially horizontal set of pinch rolls, and controllingthe speed of said second pinch roll sets to maintain said second naturalloop at a predetermined size and under very little tension.

5. An apparatus for obliquely changing the pass plane of a metal stripmoving through a processing line comprising a first and second set ofpinch rolls spaced from each other to define an intermediate pass insaid processing line, said pinch roll sets being obliquely disposed withrespect to each other to define the desired change in the pass plane,means for controlling the relative speed of said pinch rolls to maintaina tension in the strip of said intermediate pass substantially below theline tension in said processing line.

6. An apparatus as defined in claim 5 wherein said tension issubstantially zero and due primarily to the 0 weight of said metal stripin said natural loop.

7. An apparatus as defined in claim 5 wherein said means comprises adevice for sensing the transverse position of said metal strip betweensaid pinch roll sets, and a device for changing the relative speed ofsaid pinch roll sets in response to a predetermined change in thetransverse. position of said metal strip.

8. An apparatus for obliquely changing the pass plane of a metal stripmoving through a processing line from a first plane to a second planecomprising first means for forming a low tension, natural loop in saidmetal strip between said pass planes with said strip being twisted insaid loop between a substantially horizontal and a substantiallyedgewise disposition, and second means for maintaining the size of saidnatural loop within predetermined limits, said first means including afirst set of pinch rolls 'with a nip in said first plane, a second setof pinch rolls with a nip in said second plane, and said pinch rollsbeing spaced to allow the natural formation of said loop so that alllongitudinal lines in said metal strip between said roll sets aresubstantially equal.

9. An apparatus for obliquely changing the pass plane of a metal stripmoving through a processing line from a first plane to a second planecomprising first means for forming a low tension, natural loop in saidmetal strip between said pass planes with said strip being twisted insaid loop between a substantially horizontal and a substantiallyedgewise disposition, and second means for maintaining the size of saidnatural loop within predetermined limits, said second plane extending ina direction angularly disposed. with respect to said first plane.

10. An apparatus as defined in claim 9 wherein said angular dispositionis approximately 180.

11. An apparatus as defined in claim 9 wherein said angular dispositionis approximately C.

References Cited by the Examiner UNITED STATES PATENTS 1,525,939 2/1925Holmes 226-118 2,087,010 7/1937 Wardle 242-78.6 X 3,071,332 1/1963 Dain226-118 X 3,105,625 10/1963 Miserocchi 226118 X M. HENSON WOOD, 111.,Primary Examiner.

ROBERT B. REEVES, Examiner.

1. A METHOD OF CHANGING THE PASS PLANE OF A METAL STRIP MOVING THROUGH APROCESSING LINE FROM A FIRST PLANE TO A SECOND PLANE OBLIQUE TO SAIDFIRST PLANE COMPRISING THE STEPS OF GUIDING A FIRST SECTION OF SAIDMETAL STRIP ALONG SAID FIRST PLANE, DRIVING THE FIRST SECTION OF METALSTRIP AT A PREDETERMINED LINE SPEED AND UNDER LINE TENSION, GUIDING ASECOND AND SUBSEQUENT SECTION OF SAID METAL STRIP ALONG SAID SECONDPLANE, DRIVING SAID SECOND SECTION OF SAID METAL STRIP AT APREDETERMINED LINE SPEED AND UNDER LINE TENSION, FORMING A LOW TENSIONNATURAL LOOP IN SAID METAL STRIP BETWEEN SAID SECTIONS, WITH SAID STRIPTWISTED IN SAID LOOP BETWEEN A SUBSTANTIALLY HORIZONTAL AND ASUBSTANTIALLY EDGEWISE DISPOSITION AND CORRELATING THE SPEEDS OF SAIDSECTIONS TO MAINTAIN SAID NUTURAL LOOP.